What is the difference between Rotax 915 and 916

So you're trying to decide between the Rotax 915 iS and the newer 916 iS. Yeah, it's a big deal for anyone building or flying an LSA, experimental, or certified aircraft. Both are turbocharged, fuel-injected four-strokes from BRP-Rotax. But here's the thing—the 916 iS isn't just a minor update. It's a serious evolution. More power, some clever engineering, and they somehow kept the weight and external size almost the same. The real magic? The 916 iS got a bump in displacement and—this is key—an intercooler. That combo gives you a whole lot more oomph.

What are the key technical differences in displacement and power?

Let's talk numbers. The 915 iS displaces 1352 cc. The 916 iS? 1359 cc. Doesn't sound like much, right? But that tiny increase comes from a longer piston stroke. And when you pair that with a redesigned cylinder head and a turbocharger that's been reworked... well, the power difference is anything but tiny.

• Take-off Power: The 915 iS gives you 135 hp at 5800 RPM. The 916 iS cranks out 152 hp at the same RPM.
• Maximum Continuous Power: 128 hp for the 915 iS, 141 hp for the 916 iS.
• Torque: The 916 iS pulls harder down low. Better climb, shorter takeoffs. That matters.

All that extra power means the 916 iS just doesn't care about altitude, heat, or heavy loads. It keeps performing.

How does the cooling system differ between the two engines?

This is where things get really different. The 915 iS uses liquid cooling for the cylinder heads, but the cylinders themselves are air-cooled. And the turbo? No intercooler. Just raw, hot compressed air going in. The 916 iS changes the game entirely—it's got a dedicated liquid-cooled intercooler for the intake air.

That liquid-to-liquid intercooler drops the temp of the compressed air dramatically. Cooler air is denser air. Denser air means better combustion and more power without risking detonation. But it comes at a cost—the 916 iS needs a bigger radiator and a more powerful water pump to handle all that extra heat from the intercooler system.

How do the fuel and electronic systems compare?

Both engines share the same ECU and dual-channel FADEC system. But the 916 iS runs newer software—more advanced fuel maps, different ignition timing, all tuned for that higher boost and cooler intake air.

What are the maintenance and reliability considerations?

They share a lot of core stuff, so basic maintenance is similar. But the 916 iS adds complexity—a liquid-cooled intercooler, an extra water pump, more ducting. That's more stuff that can go wrong. But here's the trade-off: the intercooler keeps everything running cooler. And cooler engines tend to last longer. Pistons, valves, all that—they might actually live a happier life in the 916.

Expert Insight: The Rotax 916 iS is not just a tuned 915. It is a fundamentally re-engineered powerplant. The intercooler allows the engine to run higher boost pressures safely, which is why it produces 17 more horsepower without a significant weight penalty. For pilots operating in high-density altitude environments, the 916 is a game-changer.

Frequently Asked Questions (FAQ)

Checklist for Buyers: Key Decision Factors

• Power Requirement: Need 152 hp for a heavy plane or flying out of a high-altitude strip? 916 iS. If 135 hp does the job, the 915 iS is proven and reliable.
• Aircraft Type: The 916 iS shines in high-performance LSAs, kitplanes with big gross weights, or certified birds like the new Cessna 172. The 915 iS is perfect for standard LSA and experimental designs.
• Operating Environment: Hot and high (density altitude above 5,000 ft)? The 916 iS gives you a real safety margin. At sea level, the 915 iS is already plenty capable.
• Budget: The 916 iS costs more—like 15-20% more. And don't forget installation and possible airframe mods.
• Maintenance Access: Make sure your mechanic knows the liquid-cooled intercooler system. It's not rocket science, but it's different.